Trace detection machines are in common use at airports, prisons, immigration checkpoints, military bases, and embassies, among other places. They are used to detect trace quantities of explosives and contraband drugs on the surfaces of objects such as luggage, parcels, and clothing. The machines used for such detecting must be periodically tested to determine that the correct response is obtained. This testing serves as a measure of quality control for both the instrument and the personnel who do the sampling and testing.
However, the testing must use a carefully prepared reference sample that will produce a known and consistent response. This is done by having a known identity and quantity of a contraband substance in the test sample, otherwise the test is meaningless at best and misleading at worst. When doing this testing it is not feasible to put pure contraband substances directly on the surface of an object since the quantities involved are extremely small, typically nanogram amounts (i.e. trace amounts). At these levels the variation between amounts directly deposited could be as much as 10 to 1, with no way to determine the variation until the samples were analyzed.
One type of test involves wiping a surface suspected of being contaminated with drugs or explosives with a piece of cloth or paper. The cloth or paper is then tested in a device that uses ion mobility spectrometry, gas chromatography, chemiluminescence (thermal energy activation, or TEA), or a combination of these methods to detect the presence of drugs or explosives. In order to test and evaluate the entire system (hardware and operators) there must be a known quantity of a known substance on the surface which is picked up by the method specified by the hardware manufacturer. This requires that the contraband substance be in a form that allows it to be repeatably deposited on the surface and also repeatably removed from the surface by the cloth or paper.
In addition, when using an ion mobility spectrometer (IMS) as the detector, the carrier should be compatible with the positive ion mode as well as the negative ion mode so that both explosives and drugs can be tested for.
Accordingly, it is an object of the present invention to provide a reference sample carrier for contraband substances.
It is a further object of the present invention to provide such reference sample carrier which can be prepared in advance and stored for extended periods of time.
It is a further object of the present invention to provide such reference sample carrier that does not degrade the contraband substances contained therein.
It is a further object of the present invention to provide such reference sample carrier that does not degrade the surfaces it is placed on.
It is a further object of the present invention to provide such reference sample carrier that can be prepared from off the shelf components.
It is a further object of the present invention to provide such reference sample carrier that has the consistency of hand cream and can be dispensed from a tube or a syringe.
It is a further object of the present invention to provide such reference sample carrier that can be accurately deposited onto surfaces and leave consistent trace amounts of explosive or drug when the deposit is dried.
It is a further object of the present invention to provide such reference sample carrier that is compatible with a gas chromatograph with an ion mobility detector or a thermal energy activation detector.
It is a further object of the present invention to provide such reference sample carrier that is compatible with an ion mobility spectrometer that is being used in either the positive ion mode or the negative ion mode.
It is a further object of the present invention to provide such reference sample carrier that, when dried, can be wipe sampled and analyzed according to the instructions of the trace detection equipment manufacturer and the wipe will yield a positive analysis result.
Briefly, the present invention is a carrier for contraband substances such as explosives and narcotics which does not degrade the contraband substance or the surface on which it is placed. The carrier is intended for use with all types of detectors; when used in conjunction with an ion mobility spectrometer (IMS) the spectrometer can be used in the positive ion mode as well as in the negative ion mode. The carrier preserves the contraband substance, which allows it to be prepared in advance and stored for relatively long periods. It is comprised of off the shelf components, making it inexpensive and easy to prepare. The components are deionized water, Solugel 480, Polyfix 106, SanSurf OMC, and ethyl alcohol.